1. Field of the Invention
This invention relates to an optical information recording method and apparatus for recording information very densely at predetermined track intervals on a recording medium such as an optical disk or a magnetooptical disk.
2. Description of the Prior Art
The construction as shown in FIG. 1 of the accompanying drawings is known as an optical information recording apparatus. In FIG. 1, a laser beam emitted from a laser light source 101 is reflected by a polarizing beam splitter 102, passes through a quarter wave plate 103 and is condensed on a disk-like recording medium (disk) 105 by an objective lens 104, whereby recording is accomplished. The light reflected from the disk 105 passes through the objective lens 104 and the quarter wave plate 103 and further passes through the polarizing beam splitter 102 and through an astigmatic optical system 112, and is applied to a four-division light detector 107. In this manner, an auto-focus signal is taken and a lens driving device 105 is driven to thereby effect auto-focusing. The above-described optical system is disposed on a base plate and is called the recording head 108 as a whole.
The recording head 108 is moved radially of the disk by a head driving mechanism 109 and a head driving motor 110. The motor 110 is controlled by a motor control circuit 111 so that the recording head 108 is moved at a predetermined speed. Also, the disk 105 is rotated by a spindle motor 106, which in turn is controlled by a spindle motor control circuit 113 so that it revolves at a predetermined angular speed.
Thus, by feeding the recording head 108 at a predetermined speed and rotating the disk 105 at a predetermined speed, information may be recorded at predetermined track intervals on the disk 105.
However, in such a conventional apparatus, the mechanical accuracy of the driving portions such as the head driving device and the head driving motor has been limited, and in order to avoid any overlapped recording attributable to the eccentricity of the disk caused by the removal thereof or to the oscillation of the rotary shaft of the disk, it has been impossible to make the track intervals so narrow, and this has formed a hindrance to highly dense recording. This apparatus is such that a primary beam and a secondary beam are applied to the disk radially thereof at a predetermined interval and information is recorded by the primary beam while a guide track pre-formed on the disk or an information track recorded one revolution before is traced by the secondary beam. Accordingly, if one or several rounds of guide tracks are provided on the disk in advance, information can be recorded very densely without the fear of the overlapped recording as mentioned above.
However, providing the guide tracks on the disk in advance as described above has led to a disadvantage that the number of manufacturing steps of the disk is increased, to greatly increase the manufacturing cost thereof.